The induction of long-term potentiation (LTP) of synaptic transmission will be investigated in the subiculum of the rat. Previous studies using field recordings indicate that LTP in this area is independent of NMDA receptors. A complication in the interpretation of these results is a heterogeneity of cell types. Pyramidal cells in this are classified, based on their firing patterns, as bursting or non-bursting. Previous studies have not investigated if the observed LTP is cell-type specific. To address this discrepancy, we have made whole cell recordings from pyramidal cells of the subiculum and attempted to induce LTP by pairing EPSP with back-propagating action potentials. Our preliminary results indicate that LTP induction may be dependent on cell type. The purpose of this proposal is to determine the bases for differences in LTP induction. We will use different induction protocols to determine if LTP is dependent on the pattern of synaptic stimulation. We will also investigate the mechanism for LTP induction among cell types, primarily by determining if there is a requirement for an increase in postsynaptic calcium and the biophysical basis for any increase. Finally, we will investigate dendritic K+ channel expression and correlate any differences with the ability to induce LTP.